Pre-filled containers, such as pre-filled syringes and pre-filled cartridges, are filled by manufacturers in controlled sterile environments, eliminating the need for a patient or a medical professional to fill them from vials or ampoules prior to use. Pre-filled syringes typically have life storage of two years or more.
Auto-injectors comprising pre-filled syringes provide automation of the injection stroke, alleviating the need for the patient or medical professional to actuate a plunger rod to deliver medication.
Industry standard ‘staked needle’ pre-filled syringes, such as the BD Hypak, the Gerresheimer RTF or ClearJect, the Schott TopPak, the Daikyo Crystal Zenith® Syringe, and other commercially available glass or plastic ready to fill syringes, are commonly used as the primary pack or primary container for auto-injectors.
Historically the industry has been reliant upon these well-established off-the-shelf primary containers, usually the glass versions. Most of the alternative auto-injector technologies require a bespoke primary container, which introduces unwanted risk and cost to the development process. However, the standard glass pre-filled syringe and to a lesser extent the glass cartridge, present a number of problems.                They are fragile and not well suited to use in spring-driven auto-injector devices. A pressure spike or pulse created when the auto-injector spring hits the syringe stopper or piston can cause chipping or breakage of the syringe.        Glass is dimensionally difficult to control during syringe manufacture, so syringe tolerances are broad. This is especially true of the length, making it difficult to design an auto-injector device to fit round it.        The epoxy glue used in staked needle syringes typically used in auto-injectors can interact with the drug.        Syringe nozzles are typically formed over a tungsten pin. Residue of the tungsten pin can interact with the drug during storage.        The drug contained within a pre-filled syringe is in contact with the needle metal during prolonged storage, which can cause drug stability problems.        The drug is typically in contact with a needle metal during prolonged storage, and this requires a rubber cap, or ‘boot’, to close the opening at the needle tip. Application or removal of the rubber cap can lead to needle damage.        The container stopper or piston has four functions: drug delivery, oxygen barrier, humidity barrier and sterility barrier. This results in a need for complex multi-ribbed components that form a tight seal with the container chamber. This tight seal results in a need to lubricate the inside of the chamber, for example by siliconisation to minimize friction and to prevent the piston or stopper sticking to the chamber during long storage times.        Siliconisation (i.e. treatment with a silicone coating or oil) may cause stability problems with the drug contained in the pre-filled syringe or cartridge.        
Plastic cartridges and pre-filled syringes used as primary containers also have a number of disadvantages, which include:                They need to be manufactured in clear plastic with high oxygen barrier properties, which are always inferior to glass.        Because of the high oxygen barrier requirement, plastic pre-filled cartridges or syringes are expensive relative to glass pre-filled cartridges or syringes.        Extractables and leachables from the plastic forming the cartridge or syringe are higher than in glass containers. Extensive testing is required before they can be safely used.        The candidate plastics are not as ‘known’ as glass. This results in an industry reluctance to adopt them.        As with glass pre-filled containers, the drug contained within the pre-filled container is in contact with the needle metal during prolonged storage, which can cause drug stability problems.        The drug is typically in contact with a needle metal during prolonged storage, and this requires a rubber cap, or ‘boot’, to close the opening at the needle tip. Application or removal of the rubber cap can lead to needle damage.        
Both glass and plastics syringes can only be filled without gas bubbles if they are vacuum stoppered, which slows the filling line down considerably.
Various patents describe devices that try to overcome some of the above problems, notably the wet needle. Most of the prior art involves a completely new primary pack which the industry is reluctant to use. For instance US20120130318 A1 describes a device with a diaphragm to keep the needle dry, but which requires a completely new primary pack.
Another trend in the industry is that so called small molecule drugs, or conventional drugs, are being replaced by large molecule biopharmaceutical (biological) drugs. This trend has accelerated the need for alternative delivery systems with dry needles, reduced silicone lubrication, no tungsten residue, and good oxygen barrier properties, and in some cases larger volumes than traditionally injected.
The vast majority of biological drugs have to be administered parentally. Most protein drug formulations are destroyed by digestive enzymes if taken orally, and it is difficult to get sufficient active dosage to transfer across a mucous membrane or epithelium, so the bioavailability is typically low. All antibody drugs will be for parenteral administration for the foreseeable future. Most injections and infusions have never been particularly popular with the recipient. They hurt, or at least they are perceived to hurt especially if the needles are of large diameter.
Many biological drugs are more viscous than small molecule drugs. That makes them more difficult to inject, as either larger diameter needles are required to minimize flow resistance, or much higher pressures are required if the favoured small needles are used. This can lead to breakage of containers.
One solution is to dilute the highly viscous drug reducing its viscosity. If this is done the total volume can exceed the maximum acceptable injectable amount of about 1.5 ml. To inject larger volumes in excess of 1.5 ml, patch or bolus pumps are used.